Exemplo n.º 1
0
Arquivo: asm.go Projeto: rsc/tmp
func assemble(file string) int {
	if outfile == "" {
		outfile = strings.TrimSuffix(filepath.Base(file), ".s") + "." + string(Thechar)
	}

	of, err := os.Create(outfile)
	if err != nil {
		Yyerror("%ca: cannot create %s", Thechar, outfile)
		errorexit()
	}

	obuf = *obj.Binitw(of)
	fmt.Fprintf(&obuf, "go object %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion())
	fmt.Fprintf(&obuf, "!\n")

	var i int
	for Pass = 1; Pass <= 2; Pass++ {
		pinit(file)
		for i = 0; i < len(Dlist); i++ {
			dodefine(Dlist[i])
		}
		Yyparse()
		Cclean()
		if nerrors != 0 {
			return nerrors
		}
	}

	obj.Writeobjdirect(Ctxt, &obuf)
	obj.Bflush(&obuf)
	return 0
}
Exemplo n.º 2
0
Arquivo: lib.go Projeto: rsc/tmp
func (mode *BuildMode) Set(s string) error {
	goos := obj.Getgoos()
	goarch := obj.Getgoarch()
	badmode := func() error {
		return fmt.Errorf("buildmode %s not supported on %s/%s", s, goos, goarch)
	}
	switch s {
	default:
		return fmt.Errorf("invalid buildmode: %q", s)
	case "exe":
		*mode = BuildmodeExe
	case "c-archive":
		switch goos {
		case "darwin", "linux":
		default:
			return badmode()
		}
		*mode = BuildmodeCArchive
	case "c-shared":
		if goarch != "amd64" && goarch != "arm" {
			return badmode()
		}
		*mode = BuildmodeCShared
	case "shared":
		if goos != "linux" || goarch != "amd64" {
			return badmode()
		}
		*mode = BuildmodeShared
	}
	return nil
}
Exemplo n.º 3
0
Arquivo: lib.go Projeto: rsc/tmp
func mywhatsys() {
	goroot = obj.Getgoroot()
	goos = obj.Getgoos()
	goarch = obj.Getgoarch()

	if !strings.HasPrefix(goarch, Thestring) {
		log.Fatalf("cannot use %cc with GOARCH=%s", Thearch.Thechar, goarch)
	}
}
Exemplo n.º 4
0
Arquivo: galign.go Projeto: rsc/tmp
func main() {
	if obj.Getgoos() == "nacl" {
		resvd = append(resvd, x86.REG_BP, x86.REG_R15)
	} else if obj.Framepointer_enabled != 0 {
		resvd = append(resvd, x86.REG_BP)
	}

	gc.Thearch.Thechar = thechar
	gc.Thearch.Thestring = thestring
	gc.Thearch.Thelinkarch = thelinkarch
	gc.Thearch.Typedefs = typedefs
	gc.Thearch.REGSP = x86.REGSP
	gc.Thearch.REGCTXT = x86.REGCTXT
	gc.Thearch.REGCALLX = x86.REG_BX
	gc.Thearch.REGCALLX2 = x86.REG_AX
	gc.Thearch.REGRETURN = x86.REG_AX
	gc.Thearch.REGMIN = x86.REG_AX
	gc.Thearch.REGMAX = x86.REG_R15
	gc.Thearch.FREGMIN = x86.REG_X0
	gc.Thearch.FREGMAX = x86.REG_X15
	gc.Thearch.MAXWIDTH = MAXWIDTH
	gc.Thearch.ReservedRegs = resvd

	gc.Thearch.AddIndex = addindex
	gc.Thearch.Betypeinit = betypeinit
	gc.Thearch.Cgen_bmul = cgen_bmul
	gc.Thearch.Cgen_hmul = cgen_hmul
	gc.Thearch.Cgen_shift = cgen_shift
	gc.Thearch.Clearfat = clearfat
	gc.Thearch.Defframe = defframe
	gc.Thearch.Dodiv = dodiv
	gc.Thearch.Excise = excise
	gc.Thearch.Expandchecks = expandchecks
	gc.Thearch.Getg = getg
	gc.Thearch.Gins = gins
	gc.Thearch.Ginsboolval = ginsboolval
	gc.Thearch.Ginscon = ginscon
	gc.Thearch.Ginsnop = ginsnop
	gc.Thearch.Gmove = gmove
	gc.Thearch.Linkarchinit = linkarchinit
	gc.Thearch.Peep = peep
	gc.Thearch.Proginfo = proginfo
	gc.Thearch.Regtyp = regtyp
	gc.Thearch.Sameaddr = sameaddr
	gc.Thearch.Smallindir = smallindir
	gc.Thearch.Stackaddr = stackaddr
	gc.Thearch.Stackcopy = stackcopy
	gc.Thearch.Sudoaddable = sudoaddable
	gc.Thearch.Sudoclean = sudoclean
	gc.Thearch.Excludedregs = excludedregs
	gc.Thearch.RtoB = RtoB
	gc.Thearch.FtoB = FtoB
	gc.Thearch.BtoR = BtoR
	gc.Thearch.BtoF = BtoF
	gc.Thearch.Optoas = optoas
	gc.Thearch.Doregbits = doregbits
	gc.Thearch.Regnames = regnames

	gc.Main()
	gc.RunAtExit()
}
Exemplo n.º 5
0
Arquivo: lex.go Projeto: rsc/tmp
func importfile(f *Val, line int) {
	if f.Ctype != CTSTR {
		Yyerror("import statement not a string")
		fakeimport()
		return
	}

	if len(f.U.Sval) == 0 {
		Yyerror("import path is empty")
		fakeimport()
		return
	}

	if isbadimport(f.U.Sval) {
		fakeimport()
		return
	}

	// The package name main is no longer reserved,
	// but we reserve the import path "main" to identify
	// the main package, just as we reserve the import
	// path "math" to identify the standard math package.
	if f.U.Sval == "main" {
		Yyerror("cannot import \"main\"")
		errorexit()
	}

	if myimportpath != "" && f.U.Sval == myimportpath {
		Yyerror("import %q while compiling that package (import cycle)", f.U.Sval)
		errorexit()
	}

	if f.U.Sval == "unsafe" {
		if safemode != 0 {
			Yyerror("cannot import package unsafe")
			errorexit()
		}

		importpkg = mkpkg(f.U.Sval)
		cannedimports("unsafe.6", unsafeimport)
		imported_unsafe = 1
		return
	}

	path_ := f.U.Sval
	if islocalname(path_) {
		if path_[0] == '/' {
			Yyerror("import path cannot be absolute path")
			fakeimport()
			return
		}

		prefix := Ctxt.Pathname
		if localimport != "" {
			prefix = localimport
		}
		cleanbuf := prefix
		cleanbuf += "/"
		cleanbuf += path_
		cleanbuf = path.Clean(cleanbuf)
		path_ = cleanbuf

		if isbadimport(path_) {
			fakeimport()
			return
		}
	}

	file, found := findpkg(path_)
	if !found {
		Yyerror("can't find import: %q", f.U.Sval)
		errorexit()
	}

	importpkg = mkpkg(path_)

	// If we already saw that package, feed a dummy statement
	// to the lexer to avoid parsing export data twice.
	if importpkg.Imported != 0 {
		tag := ""
		if importpkg.Safe {
			tag = "safe"
		}

		p := fmt.Sprintf("package %s %s\n$$\n", importpkg.Name, tag)
		cannedimports(file, p)
		return
	}

	importpkg.Imported = 1

	var err error
	var imp *obj.Biobuf
	imp, err = obj.Bopenr(file)
	if err != nil {
		Yyerror("can't open import: %q: %v", f.U.Sval, err)
		errorexit()
	}

	if strings.HasSuffix(file, ".a") {
		if !skiptopkgdef(imp) {
			Yyerror("import %s: not a package file", file)
			errorexit()
		}
	}

	// check object header
	p := obj.Brdstr(imp, '\n', 1)

	if p != "empty archive" {
		if !strings.HasPrefix(p, "go object ") {
			Yyerror("import %s: not a go object file", file)
			errorexit()
		}

		q := fmt.Sprintf("%s %s %s %s", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
		if p[10:] != q {
			Warn("WARNING ONLY: import %s: object is [%s] expected [%s]", file, p[10:], q)
			//errorexit()
		}
	}

	// assume files move (get installed)
	// so don't record the full path.
	linehist(file[len(file)-len(path_)-2:], -1, 1) // acts as #pragma lib

	/*
	 * position the input right
	 * after $$ and return
	 */
	pushedio = curio

	curio.bin = imp
	curio.peekc = 0
	curio.peekc1 = 0
	curio.infile = file
	curio.nlsemi = 0
	typecheckok = 1

	var c int32
	for {
		c = int32(getc())
		if c == EOF {
			break
		}
		if c != '$' {
			continue
		}
		c = int32(getc())
		if c == EOF {
			break
		}
		if c != '$' {
			continue
		}
		return
	}

	Yyerror("no import in %q", f.U.Sval)
	unimportfile()
}
Exemplo n.º 6
0
Arquivo: lex.go Projeto: rsc/tmp
func Main() {
	defer hidePanic()

	// Allow GOARCH=thearch.thestring or GOARCH=thearch.thestringsuffix,
	// but not other values.
	p := obj.Getgoarch()

	if !strings.HasPrefix(p, Thearch.Thestring) {
		log.Fatalf("cannot use %cg with GOARCH=%s", Thearch.Thechar, p)
	}
	goarch = p

	Thearch.Linkarchinit()
	Ctxt = obj.Linknew(Thearch.Thelinkarch)
	Ctxt.Diag = Yyerror
	Ctxt.Bso = &bstdout
	bstdout = *obj.Binitw(os.Stdout)

	localpkg = mkpkg("")
	localpkg.Prefix = "\"\""

	// pseudo-package, for scoping
	builtinpkg = mkpkg("go.builtin")

	builtinpkg.Prefix = "go.builtin" // not go%2ebuiltin

	// pseudo-package, accessed by import "unsafe"
	unsafepkg = mkpkg("unsafe")

	unsafepkg.Name = "unsafe"

	// real package, referred to by generated runtime calls
	Runtimepkg = mkpkg("runtime")

	Runtimepkg.Name = "runtime"

	// pseudo-packages used in symbol tables
	gostringpkg = mkpkg("go.string")

	gostringpkg.Name = "go.string"
	gostringpkg.Prefix = "go.string" // not go%2estring

	itabpkg = mkpkg("go.itab")

	itabpkg.Name = "go.itab"
	itabpkg.Prefix = "go.itab" // not go%2eitab

	weaktypepkg = mkpkg("go.weak.type")

	weaktypepkg.Name = "go.weak.type"
	weaktypepkg.Prefix = "go.weak.type" // not go%2eweak%2etype

	typelinkpkg = mkpkg("go.typelink")
	typelinkpkg.Name = "go.typelink"
	typelinkpkg.Prefix = "go.typelink" // not go%2etypelink

	trackpkg = mkpkg("go.track")

	trackpkg.Name = "go.track"
	trackpkg.Prefix = "go.track" // not go%2etrack

	typepkg = mkpkg("type")

	typepkg.Name = "type"

	goroot = obj.Getgoroot()
	goos = obj.Getgoos()

	Nacl = goos == "nacl"
	if Nacl {
		flag_largemodel = 1
	}

	outfile = ""
	obj.Flagcount("+", "compiling runtime", &compiling_runtime)
	obj.Flagcount("%", "debug non-static initializers", &Debug['%'])
	obj.Flagcount("A", "for bootstrapping, allow 'any' type", &Debug['A'])
	obj.Flagcount("B", "disable bounds checking", &Debug['B'])
	obj.Flagstr("D", "path: set relative path for local imports", &localimport)
	obj.Flagcount("E", "debug symbol export", &Debug['E'])
	obj.Flagfn1("I", "dir: add dir to import search path", addidir)
	obj.Flagcount("K", "debug missing line numbers", &Debug['K'])
	obj.Flagcount("L", "use full (long) path in error messages", &Debug['L'])
	obj.Flagcount("M", "debug move generation", &Debug['M'])
	obj.Flagcount("N", "disable optimizations", &Debug['N'])
	obj.Flagcount("P", "debug peephole optimizer", &Debug['P'])
	obj.Flagcount("R", "debug register optimizer", &Debug['R'])
	obj.Flagcount("S", "print assembly listing", &Debug['S'])
	obj.Flagfn0("V", "print compiler version", doversion)
	obj.Flagcount("W", "debug parse tree after type checking", &Debug['W'])
	obj.Flagstr("asmhdr", "file: write assembly header to named file", &asmhdr)
	obj.Flagcount("complete", "compiling complete package (no C or assembly)", &pure_go)
	obj.Flagstr("d", "list: print debug information about items in list", &debugstr)
	obj.Flagcount("e", "no limit on number of errors reported", &Debug['e'])
	obj.Flagcount("f", "debug stack frames", &Debug['f'])
	obj.Flagcount("g", "debug code generation", &Debug['g'])
	obj.Flagcount("h", "halt on error", &Debug['h'])
	obj.Flagcount("i", "debug line number stack", &Debug['i'])
	obj.Flagstr("installsuffix", "pkg directory suffix", &flag_installsuffix)
	obj.Flagcount("j", "debug runtime-initialized variables", &Debug['j'])
	obj.Flagcount("l", "disable inlining", &Debug['l'])
	obj.Flagcount("live", "debug liveness analysis", &debuglive)
	obj.Flagcount("m", "print optimization decisions", &Debug['m'])
	obj.Flagcount("nolocalimports", "reject local (relative) imports", &nolocalimports)
	obj.Flagstr("o", "obj: set output file", &outfile)
	obj.Flagstr("p", "path: set expected package import path", &myimportpath)
	obj.Flagcount("pack", "write package file instead of object file", &writearchive)
	obj.Flagcount("r", "debug generated wrappers", &Debug['r'])
	obj.Flagcount("race", "enable race detector", &flag_race)
	obj.Flagcount("s", "warn about composite literals that can be simplified", &Debug['s'])
	obj.Flagstr("trimpath", "prefix: remove prefix from recorded source file paths", &Ctxt.LineHist.TrimPathPrefix)
	obj.Flagcount("u", "reject unsafe code", &safemode)
	obj.Flagcount("v", "increase debug verbosity", &Debug['v'])
	obj.Flagcount("w", "debug type checking", &Debug['w'])
	use_writebarrier = 1
	obj.Flagcount("wb", "enable write barrier", &use_writebarrier)
	obj.Flagcount("x", "debug lexer", &Debug['x'])
	obj.Flagcount("y", "debug declarations in canned imports (with -d)", &Debug['y'])
	var flag_shared int
	var flag_dynlink bool
	if Thearch.Thechar == '6' {
		obj.Flagcount("largemodel", "generate code that assumes a large memory model", &flag_largemodel)
		obj.Flagcount("shared", "generate code that can be linked into a shared library", &flag_shared)
		flag.BoolVar(&flag_dynlink, "dynlink", false, "support references to Go symbols defined in other shared libraries")
	}
	obj.Flagstr("cpuprofile", "file: write cpu profile to file", &cpuprofile)
	obj.Flagstr("memprofile", "file: write memory profile to file", &memprofile)
	obj.Flagint64("memprofilerate", "set runtime.MemProfileRate", &memprofilerate)
	obj.Flagparse(usage)

	if flag_dynlink {
		flag_shared = 1
	}
	Ctxt.Flag_shared = int32(flag_shared)
	Ctxt.Flag_dynlink = flag_dynlink

	Ctxt.Debugasm = int32(Debug['S'])
	Ctxt.Debugvlog = int32(Debug['v'])

	if flag.NArg() < 1 {
		usage()
	}

	startProfile()

	if flag_race != 0 {
		racepkg = mkpkg("runtime/race")
		racepkg.Name = "race"
	}

	// parse -d argument
	if debugstr != "" {
	Split:
		for _, name := range strings.Split(debugstr, ",") {
			if name == "" {
				continue
			}
			val := 1
			if i := strings.Index(name, "="); i >= 0 {
				var err error
				val, err = strconv.Atoi(name[i+1:])
				if err != nil {
					log.Fatalf("invalid debug value %v", name)
				}
				name = name[:i]
			}
			for _, t := range debugtab {
				if t.name == name {
					if t.val != nil {
						*t.val = val
						continue Split
					}
				}
			}
			log.Fatalf("unknown debug key -d %s\n", name)
		}
	}

	// enable inlining.  for now:
	//	default: inlining on.  (debug['l'] == 1)
	//	-l: inlining off  (debug['l'] == 0)
	//	-ll, -lll: inlining on again, with extra debugging (debug['l'] > 1)
	if Debug['l'] <= 1 {
		Debug['l'] = 1 - Debug['l']
	}

	Thearch.Betypeinit()
	if Widthptr == 0 {
		Fatal("betypeinit failed")
	}

	lexinit()
	typeinit()
	lexinit1()
	// TODO(rsc): Restore yytinit?

	blockgen = 1
	dclcontext = PEXTERN
	nerrors = 0
	lexlineno = 1

	for _, infile = range flag.Args() {
		linehist(infile, 0, 0)

		curio.infile = infile
		var err error
		curio.bin, err = obj.Bopenr(infile)
		if err != nil {
			fmt.Printf("open %s: %v\n", infile, err)
			errorexit()
		}

		curio.peekc = 0
		curio.peekc1 = 0
		curio.nlsemi = 0
		curio.eofnl = 0
		curio.last = 0

		// Skip initial BOM if present.
		if obj.Bgetrune(curio.bin) != obj.BOM {
			obj.Bungetrune(curio.bin)
		}

		block = 1
		iota_ = -1000000

		imported_unsafe = 0

		yyparse()
		if nsyntaxerrors != 0 {
			errorexit()
		}

		linehist("<pop>", 0, 0)
		if curio.bin != nil {
			obj.Bterm(curio.bin)
		}
	}

	testdclstack()
	mkpackage(localpkg.Name) // final import not used checks
	lexfini()

	typecheckok = 1
	if Debug['f'] != 0 {
		frame(1)
	}

	// Process top-level declarations in phases.

	// Phase 1: const, type, and names and types of funcs.
	//   This will gather all the information about types
	//   and methods but doesn't depend on any of it.
	defercheckwidth()

	for l := xtop; l != nil; l = l.Next {
		if l.N.Op != ODCL && l.N.Op != OAS {
			typecheck(&l.N, Etop)
		}
	}

	// Phase 2: Variable assignments.
	//   To check interface assignments, depends on phase 1.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCL || l.N.Op == OAS {
			typecheck(&l.N, Etop)
		}
	}
	resumecheckwidth()

	// Phase 3: Type check function bodies.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC || l.N.Op == OCLOSURE {
			Curfn = l.N
			decldepth = 1
			saveerrors()
			typechecklist(l.N.Nbody, Etop)
			checkreturn(l.N)
			if nerrors != 0 {
				l.N.Nbody = nil // type errors; do not compile
			}
		}
	}

	// Phase 4: Decide how to capture closed variables.
	// This needs to run before escape analysis,
	// because variables captured by value do not escape.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC && l.N.Closure != nil {
			Curfn = l.N
			capturevars(l.N)
		}
	}

	Curfn = nil

	if nsavederrors+nerrors != 0 {
		errorexit()
	}

	// Phase 5: Inlining
	if Debug['l'] > 1 {
		// Typecheck imported function bodies if debug['l'] > 1,
		// otherwise lazily when used or re-exported.
		for l := importlist; l != nil; l = l.Next {
			if l.N.Func.Inl != nil {
				saveerrors()
				typecheckinl(l.N)
			}
		}

		if nsavederrors+nerrors != 0 {
			errorexit()
		}
	}

	if Debug['l'] != 0 {
		// Find functions that can be inlined and clone them before walk expands them.
		visitBottomUp(xtop, func(list *NodeList, recursive bool) {
			for l := list; l != nil; l = l.Next {
				if l.N.Op == ODCLFUNC {
					caninl(l.N)
					inlcalls(l.N)
				}
			}
		})
	}

	// Phase 6: Escape analysis.
	// Required for moving heap allocations onto stack,
	// which in turn is required by the closure implementation,
	// which stores the addresses of stack variables into the closure.
	// If the closure does not escape, it needs to be on the stack
	// or else the stack copier will not update it.
	escapes(xtop)

	// Escape analysis moved escaped values off stack.
	// Move large values off stack too.
	movelarge(xtop)

	// Phase 7: Transform closure bodies to properly reference captured variables.
	// This needs to happen before walk, because closures must be transformed
	// before walk reaches a call of a closure.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC && l.N.Closure != nil {
			Curfn = l.N
			transformclosure(l.N)
		}
	}

	Curfn = nil

	// Phase 8: Compile top level functions.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC {
			funccompile(l.N)
		}
	}

	if nsavederrors+nerrors == 0 {
		fninit(xtop)
	}

	// Phase 9: Check external declarations.
	for l := externdcl; l != nil; l = l.Next {
		if l.N.Op == ONAME {
			typecheck(&l.N, Erv)
		}
	}

	if nerrors+nsavederrors != 0 {
		errorexit()
	}

	dumpobj()

	if asmhdr != "" {
		dumpasmhdr()
	}

	if nerrors+nsavederrors != 0 {
		errorexit()
	}

	Flusherrors()
}
Exemplo n.º 7
0
Arquivo: obj.go Projeto: rsc/tmp
func dumpobj() {
	var err error
	bout, err = obj.Bopenw(outfile)
	if err != nil {
		Flusherrors()
		fmt.Printf("can't create %s: %v\n", outfile, err)
		errorexit()
	}

	startobj := int64(0)
	var arhdr [ArhdrSize]byte
	if writearchive != 0 {
		obj.Bwritestring(bout, "!<arch>\n")
		arhdr = [ArhdrSize]byte{}
		obj.Bwrite(bout, arhdr[:])
		startobj = obj.Boffset(bout)
	}

	fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
	dumpexport()

	if writearchive != 0 {
		obj.Bflush(bout)
		size := obj.Boffset(bout) - startobj
		if size&1 != 0 {
			obj.Bputc(bout, 0)
		}
		obj.Bseek(bout, startobj-ArhdrSize, 0)
		formathdr(arhdr[:], "__.PKGDEF", size)
		obj.Bwrite(bout, arhdr[:])
		obj.Bflush(bout)

		obj.Bseek(bout, startobj+size+(size&1), 0)
		arhdr = [ArhdrSize]byte{}
		obj.Bwrite(bout, arhdr[:])
		startobj = obj.Boffset(bout)
		fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
	}

	if pragcgobuf != "" {
		if writearchive != 0 {
			// write empty export section; must be before cgo section
			fmt.Fprintf(bout, "\n$$\n\n$$\n\n")
		}

		fmt.Fprintf(bout, "\n$$  // cgo\n")
		fmt.Fprintf(bout, "%s\n$$\n\n", pragcgobuf)
	}

	fmt.Fprintf(bout, "\n!\n")

	var externs *NodeList
	if externdcl != nil {
		externs = externdcl.End
	}

	dumpglobls()
	dumptypestructs()

	// Dump extra globals.
	tmp := externdcl

	if externs != nil {
		externdcl = externs.Next
	}
	dumpglobls()
	externdcl = tmp

	zero := Pkglookup("zerovalue", Runtimepkg)
	ggloblsym(zero, int32(zerosize), obj.DUPOK|obj.RODATA)

	dumpdata()
	obj.Writeobjdirect(Ctxt, bout)

	if writearchive != 0 {
		obj.Bflush(bout)
		size := obj.Boffset(bout) - startobj
		if size&1 != 0 {
			obj.Bputc(bout, 0)
		}
		obj.Bseek(bout, startobj-ArhdrSize, 0)
		name := fmt.Sprintf("_go_.%c", Thearch.Thechar)
		formathdr(arhdr[:], name, size)
		obj.Bwrite(bout, arhdr[:])
	}

	obj.Bterm(bout)
}
Exemplo n.º 8
0
Arquivo: sym.go Projeto: rsc/tmp
func linknew(arch *LinkArch) *Link {
	ctxt := new(Link)
	ctxt.Hash = make(map[symVer]*LSym)
	ctxt.Arch = arch
	ctxt.Version = obj.HistVersion
	ctxt.Goroot = obj.Getgoroot()

	p := obj.Getgoarch()
	if p != arch.Name {
		log.Fatalf("invalid goarch %s (want %s)", p, arch.Name)
	}

	var buf string
	buf, _ = os.Getwd()
	if buf == "" {
		buf = "/???"
	}
	buf = filepath.ToSlash(buf)

	ctxt.Headtype = headtype(obj.Getgoos())
	if ctxt.Headtype < 0 {
		log.Fatalf("unknown goos %s", obj.Getgoos())
	}

	// Record thread-local storage offset.
	// TODO(rsc): Move tlsoffset back into the linker.
	switch ctxt.Headtype {
	default:
		log.Fatalf("unknown thread-local storage offset for %s", Headstr(ctxt.Headtype))

	case obj.Hplan9, obj.Hwindows:
		break

		/*
		 * ELF uses TLS offset negative from FS.
		 * Translate 0(FS) and 8(FS) into -16(FS) and -8(FS).
		 * Known to low-level assembly in package runtime and runtime/cgo.
		 */
	case obj.Hlinux,
		obj.Hfreebsd,
		obj.Hnetbsd,
		obj.Hopenbsd,
		obj.Hdragonfly,
		obj.Hsolaris:
		ctxt.Tlsoffset = -1 * ctxt.Arch.Ptrsize

	case obj.Hnacl:
		switch ctxt.Arch.Thechar {
		default:
			log.Fatalf("unknown thread-local storage offset for nacl/%s", ctxt.Arch.Name)

		case '5':
			ctxt.Tlsoffset = 0

		case '6':
			ctxt.Tlsoffset = 0

		case '8':
			ctxt.Tlsoffset = -8
		}

		/*
		 * OS X system constants - offset from 0(GS) to our TLS.
		 * Explained in ../../runtime/cgo/gcc_darwin_*.c.
		 */
	case obj.Hdarwin:
		switch ctxt.Arch.Thechar {
		default:
			log.Fatalf("unknown thread-local storage offset for darwin/%s", ctxt.Arch.Name)

		case '5':
			ctxt.Tlsoffset = 0 // dummy value, not needed

		case '6':
			ctxt.Tlsoffset = 0x8a0

		case '7':
			ctxt.Tlsoffset = 0 // dummy value, not needed

		case '8':
			ctxt.Tlsoffset = 0x468
		}
	}

	// On arm, record goarm.
	if ctxt.Arch.Thechar == '5' {
		p := obj.Getgoarm()
		if p != "" {
			ctxt.Goarm = int32(obj.Atoi(p))
		} else {
			ctxt.Goarm = 6
		}
	}

	return ctxt
}